Production of stable salts of dimethyl-p-aminophenol and p-oxyphenyltrimethylammonium.



UNITED STATES PATENT @FFTQE JAN LAGUTT, OF BASEL, SWITZERLAND, ASSIGNOR TO CHEMISGHE FABRIK VORMALS SANDOZ, OF BASEL, SWITZERLAND, A CORPORATION OF SWITZERLAND.

PRODUCTION OF STABLE SALTS OF DIMETHYL-P-AMINOPHENOL AND P-OXYPI-IENYL- Patented une 22, 1915.

TRIME'IHYLAMM ONIUM.

1 144 141 Specification of Letters Patent.

No Drawing.

To all 00h 0m it may concern Be it known that I, J AN LAGUTT, Ph. 1)., a citizen of the Swiss Republic, residing at Basel, Switzerland, have invented new and useful Improvements in the Production of Stable Salts of Dimethyl-P-Aminophenol and P-Oxyphenylti'imethylammonium, of which the following is a specification.

In the methylation of p-aminophenol considerable quantities of a mixture of dimethyluauninophenol and a compound of p-oxyphenyltrimethylammonium such as p-oxyphenyltrimethylammoniumhydroxid, are always formed besides the monomethyl-paminophenol (metol) which is the Valued photographic developer.

Although the suitability of the dimethylp-aminophenolas a developer was recognized as far back as the German patent specification No. 69,582 this body has not up to the present found employment in photography because great difi'iculties are encountered in isolating it from the methylation products of p-aminophenolowing to the easy solubility of its salts and their tendency to oxidize. Similar conditions hinder the separation of the p-oxyphenyltrimethylammonium compounds.

My experiments have shown that both dimethyl-p-aminophenol and p-oxyphenyltrimethylammonium compounds can be very conveniently isolated from solutions of their salts by adding ferrocyanids to said solutions and acidifying strongly; the acid hydro-ferrocyanid salts of the composition,

separate out very quickly and completely. P-aminophenol and mOnOmethyLp-ammophenol on the contrary glve no precipitates and with ferrocyanids in acid solution.

Application filed August 31, 1914. Serial No. 859,294.

alkaline) with a suitable organic solvent, to

remove the dimethyl-p-aminophenol, and then separating the pure ferrocyanids respectively from the residue and the extract.

In order to illustrate the new process more fully, the following examples are given:

Example 1: To a mixture resulting from the methylation of 100 kilos of p-aminophenol, which mixture besides dimethyl-paminophenol and p-oXyphenyltrimethyl-ammonium compounds may contain monomethyl-p-aminophenol and unaltered p-aminophenol in the form of their mineral acid sal 'ssolved in about 500 liters of water, add a co centrated solution of 60 kilos of crystallize potassium ferrocyanid and acidify with sulfuric acid until a strongly acid reaction is obtained on Congo paper. The acid ferrocyanids of the dimethyl-p-aminophenol and p-oxyphenyltrimethylammonium separate out as a fine, shining crystalline powder. \Vhen a filtered test portion gives no further precipitation on addition of further potassium ferrocyanid, the liquid is left to stand for about 12 hours longer to complete the crystallization. The precipitate is then filtered off and washed with a little cold water.

It may here be mentioned that alkali ferricyanids also separate the acid ferrocyanids of dimethyl-p-aminophenol and p-oxyphenyltrimethylammonium from acid solutions of these two bases with simultaneous partial oxidation of the same.

Example 2: 100 kilos of the mixture of acid ferrocyanids of dimethyl-p-aminophe- 1101 and p-oxyphenyltr1methyl-ammon1um obtained according to Example 1 are stlrred into 3 kilos of sodium hydrosulfite and 30 0 liters of water, and caustic soda solution 1s added until a weak alkaline reaction 1s ust perceptible on brilliant yellow paper. The dimeth'yl-p-aminophenol is then extracted by shaking with 200 kilos of benzene, the base being removed from the benzene extract from time to time by dilute sulfuric acid, and the extraction continued up to complete exhaustion of the initial solution which is always kept weakly alkaline. Three agitations with benzene are generally sufficient. The remaining solution then only contains p-oxyphenyltrimethylanunompm and sodium ferrocyanid, and on acidifying it with a mineral acid, pure ferrocyanid of the composition,

is precipitated in fine, shining, yellowishwhite plates. Incineration gave 15.50% Fe. ,O,; calculated amount 15.44%.

The acid extracts'of the benzene extract yield on precipitation with about 55 kilos of ferrocyanid of potassium and subsequent acidification, pure acid ferrocyanid of dimethyl-p-aminophenol,

This salt crystallizes out .of not too concentrated solutions in shining yellowish- White plates. Incineration showed 16.20% F6 0,; calculated amount 16.32%.

The extraction of the dimethyl-p-aminophenol can also be performed. with other suitable organic solvents, as for example ether.

Both the ferrocyanids are very difiicultly soluble in cold water, but dissolve easily in hot water. On boiling the aqueous solutions, decomposition occurs with splitting off of prussic acid, so that temperatures greater than C. must be avoided in recrystalliz- From the ferrocyanid obtainable by the above processes the corresponding bases can be isolated and transformed into other pure salts by known methods of conversion. Thus for example the sulfate of dimethyl-paminophenol,

can be obtained as a white crystalline powder ganic solvent substantially as and for the purpose described.

3. The process of producing the acid. ferrocyanids of dimethyl-p-aminoph'enol and p-oxyphenyltrimethylammonium which comprises precipitating such salts from a mineral acid solution containing dimethyl-paminophenol and p-oxyphenyltrimethylammonium compound, then separating said salts by extracting an alkaline solution of said precipitated salts with a suitable organic solvent and then precipitating the acid ferrocyanid of dimethyl-p-aminophenol from said extract, substantially as and for the purpose described.

l. The improvement in the art of producing the acid ferrocyanids of dimethyl-paminophenol and p-oxyphenyltrimethylammonium which comprises precipitating such salts by adding ferrocyanid to a mineral acid solution containing dimethyl-p-aminophenol and p-oxyphenyltrimethylammonium compound, substantially as and for the purpose described.

5. As a new product, the crystalline substance capable of being produced by precipitation from an acid solution containing dimethyl-p-aminophenol by means of ferro- .cyanid and comprising the acid ferrocyanid of dimethyl-p-aminophenol substantially as and for the purpose described.

6. As a new product the crystalline substance comprising the acid, ferrocyanid of dimethyl p aminophenol crystallizing in shining yellow-white probably the formula:

,In testimony whereof I have hereunto set 110 plates and having 

